Hydraulic hammers are widely used on work sites to break up or demolish large hard objects, such as, rocks, concrete, asphalt, frozen ground, etc., before such objects can be moved away. Hydraulic hammers can be mounted to work machines like back hoes or excavators, or they can be hand-held. In operation, high pressure fluid drives a piston of the hydraulic hammer to strike a work tool, such as a tool bit, which then strikes the hard object to be broken.
Generally speaking, the work tool is retained within a lower and an upper bushing of the hydraulic hammer, and the upper and the lower bushings in turn are enclosed within a bore of a sleeve or housing, also commonly referred to as a front head. Because of repeated impact of the work tool on hard objects, the lower bushing of the hydraulic hammer experiences extreme loads during operation. Such extreme loads often cause the lower bushing to wear out. As such, the lower bushing may need to be replaced or serviced several times during the product life of the hydraulic hammer. In order to remove the lower bushing from the front head, a cross pin connecting the front head and the lower bushing together may be detached and, the lower bushing may be pulled or pushed out from the front head for replacement or for servicing.
Conventionally, the outer surface of the lower bushing and an inner surface of the bore of the front head are designed parallel to each other such that when the lower bushing is pushed (or pulled) out for removal from the front head, the clearance between the lower bushing and the front head remains the same until the lower bushing is completely removed from the front head bore. As this clearance is small, contact between the lower bushing and the front head may occur, thereby making the removal of the lower bushing difficult. In certain instances, the lower bushing may change its shape during usage, causing the surfaces of the lower bushing and the front head to bind during removal, thereby exacerbating the removal process of the lower bushing. This difficulty in removing the lower bushing from the front head not only increases the servicing time of the lower bushing, it also adds to the labor cost and may even corrode the front head somewhat, which in turn may lead to replacement of the hydraulic hammer altogether.
It would accordingly be beneficial if an improved mechanism for effectively removing the lower bushing from the front head were developed. It would additionally be beneficial if such a mechanism avoided contact between the front head and the lower bushing during removal.